1. Field of the Invention
The present invention relates to foods and beverages containing lactate monooxygenase. Foods, beverages and various table luxuries (hereinafter collectively referred to as foods and beverages) deteriorate in quality during distribution and storage. One major cause of this problem is that even if foods and beverages are sealed in containers, they are subject to oxidative deterioration, i.e., direct or indirect oxidation of their components by oxygen that is present in the head space of the container or dissolved in the contents. The present invention is principally intended to provide foods and beverages in which lactate monooxygenase is incorporated so as to prevent deterioration of their quality by causing oxygen to be eliminated therefrom rapidly and in a safe way.
Browning, which is one of the forms of oxygenassociated deterioration of foods and beverages, is known to involve the reaction that accompanies oxidation of ascorbic acid and the reaction caused by phenolase. In the former reaction, browning is triggered by oxidation of ascorbic acid, which is promoted either by direct oxidation with dissolved oxygen or by the catalytic action of ascorbate oxidase. In the second type of reaction which involves phenolase, oxygen participates in the reaction as a substrate whether the phenolase is cresolase which hydroxylates monophenols or catecholase which accelerates the oxidation of diphenol that is produced by the action of cresolase. The oxidation caused by either mechanism causes many of the food components to become involved in various chain reactions including nonenzymatic reactions such as the Maillard reaction, thereby deteriorating the quality of the subject foods and beverages.
Oxidative deterioration of foods and beverages involving browning generally causes problems in terms of both appearance and flavor. For instance, the organoleptic deterioration of beer is known to have a high degree of correlation with the concentration of dissolved oxygen in the beer. Thus, the duration of time in which brewed beer can be stored while retaining its high quality is dependent on how low the concentration of dissolved oxygen in beer can be maintained.
It has recently been shown by many studies that free radicals including active oxygen take part in the process of aging, cancer development and inflammation in mammals including the human being. Specific examples of active oxygen include superoxide anion radical (O.sub.2.sup.--), hydrogen peroxide (H.sub.2 O.sub.2) and hydroxyradical (OH.sub.--). These species are molecules of triplet oxygen with one, two or three electrons reduced, and singlet oxygen (.sup.1 O.sub.2). All of them are highly reactive molecular species that damage nucleic acids and other cellular components and which hence are deleterious to human health. This problem has recently come into the spotlight as a result of successive publication of reports that show the presence of hydrogen peroxide in foods, beverages and various table luxuries. The source of ths hydrogen peroxide has been identified as dissolved oxygen by the present inventors (Suwa, Y. et al., "The Enzymatic Inactivation of Oxygen-Dependent Mutagenicity of Coffee" in Proc. 4th Intern. Conf. Environ. Mutagens, 262, 1985).
It would therefore be very important to remove oxygen from foods and beverages for the purpose of improving the organoleptic and other aspects of their quality and reducing their potential risk to human health. Prior Art:
Oxidases such as glucose oxidase and ascorbate oxidase are commonly employed as enzymes for removing oxygen from foods and beverages. The reaction scheme of deoxygenation by glucose oxidase is shown below, from which one can see that oxidases generate hydrogen peroxide via the superoxide anion (O.sub.2.sup.--), thereby causing problems not only to the quality control of foods and beverages of interest but also to the health of humans who ultimately consume them. ##STR1##
When a certain additive is employed to remove oxygen from foods and beverages, it is vitally important to ensure safety of not only the additive itself but also the product that is formed as a result of the deoxygenation reaction.